URL: http://www.openajax.org/member/wiki/IDE_Issue_1
IDE Issue 1: Toolkit identification, configuration, loading, and
initialization
Original write-up
Most of the widgets that we are looking to use with IDEs are built on top
of an Ajax toolkit. For example, in 3 early samples, we looked into the
date picker widget (built on Dojo), a menu widget (built on YUI), and a
Google Map widget (built on Google-developed JavaScript). In most cases,
one or more Ajax libraries need to be sourced into the HTML application via
a <script> tag and (in some cases) some sort of library configuration and
initialization must occur for the widget to work properly when deployed
with the HTML page.
The question is what information will we include within our IDE standards
around toolkit identification, configuration, loading and initialization.
On one extreme, we could decide to steer clear of defining any standards in
this area and decide that the various IDEs must take care of this somehow
or other. On the other extreme, we could decide to define an industry
standard for how widgets identifier the Ajax libraries that they need and
how those libraries are configured, loaded and initialized.
Existing industry practice
jMaki's widget.json file includes a config property that provides
information about toolkits and how they should be initialized. Here is a
snippet from the information within jMaki for the Dojo date picker widget:
'config' : {
'type' :
{ 'id' : 'dojo',
'libs' : [
'../resources/libs/dojo/v0.4.3/djd43.js'
],
'preload' : 'if (typeof djConfig ==\'undefined\') djConfig =
{ parseWidgets: false, searchIds: [] };',
'resources' : [
'../resources/libs/dojo/v0.4.3/src'
]
},
The jMaki engineers need to explain this in more detail, but a good guess
is that libs: points to the root JavaScript file to load for Dojo, preload:
provides configuration settings that are used once the Dojo file is loaded
via a dynamic <script> tag, and resources: is the root folder for finding
other resources needed by Dojo.
Adobe Dreamweaver proposes an <assetfile type="javascript"
location="<url>"> tag to identify JavaScript files that need to be loaded.
Complexities that we might want (or not) to address
Here are some sub-issues about various complexities that we might want to
address:
Shared use of Ajax libraries - If two widgets use the same Ajax
library, we might want to (or in fact need to) ensure that the Ajax
library is loaded only once and that the two widgets share the same
instance of the given library. This begs the following question:
What happens if widgets use different variations of the same
Ajax library? - Suppose one widget requires jQuery 1.5 and
another one jQuery 2.3 and there is a major incompatibility
between jQuery 1.x and 2.x. Suppose one widget ships with a
custom version of Dojo 1.0 that only supports the features
needed by that widget and another widget uses a different
custom version of Dojo. (Most likely we will have to have some
reasonable behavior rules on Ajax toolkits, such as what we see
in the introduction chapter to the OpenAjax Hub 1.0
Specification.)
Dynamic loading standards for Ajax libraries - There have been at
least two recent proposals to OpenAjax Alliance about having us
define a standard JavaScript loader. OpenAjax Alliance hasn't taken a
run at that issue yet.
Analysis
It seems like an IDE loses much of its value as a visual UI tool if it
cannot automatically insert <script> tags for the necessary Ajax libraries
automatically into the Web page on behalf of the user. (Same argument for
other resources such as <link> tags pointing to CSS files.) For a
reasonable user experience, one would hope that a user does not need to do
any more than:
Identify an Ajax library that they want to use with their
application, and thereby have the IDE make all of the widgets from
that library available to the user
Import specific widgets from that library into the HTML document,
such as via drag-and-drop
Customize those widgets, such as with a property inspector
Therefore, due to a strong user requirement, we are strongly inclined to
provide some automation in the area of automatic loading of Ajax libraries
from within the IDE.
Many common Ajax libraries have an architecture that would allow some level
of automation in this area. It is common that a library has a base set of
JavaScript such that it is possible to:
first load the base set of JavaScript for a given library
then load the specific JavaScript for each widget used on the Web
page
(Note: some Ajax libraries have packaging features, such as dojo.require,
that allow consolidation of JavaScript into a single file.)
Both jMaki and Dreamweaver have had some degrees of successful with popular
Ajax libraries in this area.
Given the strong benefit to the user and the fact that many Ajax libraries
have a reasonably desirable architecture in this area, it seems like we
should pursue standardization.
Alternative approaches
Strawman widget metadata
The strawman proposal simply identifies a library by name and version.
<widget
libraryName="dojo"
libraryVersion="0.4.3"
>
jMaki widget metadata
jMaki identifies the library by name and points to the JavaScript files.
jMaki also includes configuration information (i.e., djConfig).
'config' : {
'type' :
{ 'id' : 'dojo',
'libs' : [
'../resources/libs/dojo/v0.4.3/djd43.js'
],
'preload' : 'if (typeof djConfig ==\'undefined\') djConfig =
{ parseWidgets: false, searchIds: [] };',
'resources' : [
'../resources/libs/dojo/v0.4.3/src'
]
},
Adobe Dreamweaver metadata
Adobe proposes an <assetfile location="..." referenceType="javascript"/>
tag to identify the JavaScript that needs to be loaded"
<assetfiles>
<!-- the following asset files will get copied to the users's site
when they save their document and the paths will be adjust to point to them
-->
<!-- Specifing referenceType (link, import, or javascript) will create
a reference to the associated asset file in the <head> -->
<!-- not specifying a referencetype copies the file but adds no
reference to it -->
<assetfile location="yui/2.3.1/build/menu/assets/skins/sam/menu.css"
referenceType="link"/>
<assetfile location="yui/2.3.1/build/fonts/fonts-min.css"
destination="yui/build/fonts/fonts-min.css" referenceType="link"/>
<assetfile location="yui/2.3.1
/build/yahoo-dom-event/yahoo-dom-event.js" referenceType="javascript"/>
<assetfile location="yui/2.3.1/build/container/container_core-min.js"
referenceType="javascript"/>
<assetfile location="yui/2.3.1/build/menu/menu-min.js"
referenceType="javascript"/>
<assetfile location="yui/2.3.1/build/menu/map.gif" />
</assetfiles>
Jon's proposed resolution
Specific recommendations:
Only focus on workflows where there is only a single version of a
given Ajax library used within a particular HTML page. For example,
our primary target workflow would be situations where the entire page
uses a single version of a particular library (e.g., Dojo 3.1 or YUI
1.9), but don't attempt to define metadata markup that address the
ability to mix Dojo 0.4 widgets with Dojo 1.0 widgets. Assume that if
a user needs a new widget from a newer version of a given library
(e.g., Dojo 1.0's grid widget), then the user has to upgrade the
entire page to the newer version of the library.
NOTE: By saying only focus, that just means where we focus. It
doesn't necessarily mean that we don't allow other workflows.
Choose a markup approach similar to Adobe's <assetfile> that lists
various widget-specific files (including the library's core
JavaScript) that need to be loaded within the <head> of the HTML
page. The idea is that, in general, each <assetfile> would result in
the addition of a single line of code to the HTML page, such as a
<script> tag or <link> tag.
NOTE: This simple approach neither requires that Ajax libraries
and IDEs support this metadata nor restricts Ajax libraries and
IDEs from supporting other similar mechanisms. If this simple
approach is not sufficient for particular requirements, Ajax
libraries and IDEs are fully free to invent their own
mechanisms.
NOTE: If multiple widgets point to the same asset files, assume
the IDEs will be smart enough to only load the given assets
once.
NOTE: We might consider a feature where OpenAjaxLibrary.xml
also supports something similar to <assetfile> for any files
that must be loaded in order for any of the widgets to work.
NOTE: We need to think through how this might relate to a
possible future OpenAjax standard around centralized JavaScript
loading.
Define XML metadata markup that provides similar hooks to jMaki's
libs, preload, and resources, which means markup that identifies the
location of the JavaScript files to load for a given library, any
JavaScript to execute before loading that library, and the location
of the root directory for that library.
NOTE: Regarding resources, perhaps that belongs in
OpenAjaxLibrary.xml instead.
NOTE: Regarding preload, maybe we need a library-level preload
instruction within OpenAjaxLibrary.xml along with widget-level
preload instructions within the widget metadata.
Here is some markup that would address the bullets listed above:
Within OpenAjaxLibrary.xml:
<library xmlns="http://ns.openajax.org/library"
...
baseDirectory="...relative URL to root folder for library..."
...
>
...
<assetfiles>
<assetfile type="javascript|css|..." location="<url>"/> <!-- from Adobe
-->
<!-- etc -->
</assetfiles>
...
<preload> <!-- from jMaki -->
...javascript logic...
</preload>
...
</library>
Within OpenAjaxWidget.xml:
<widget xmlns="http://ns.openajax.org/widget" ...>
...
<assetfiles>
<assetfile type="javascript|css|..." location="<url>"/> <!-- from Adobe
-->
<!-- etc -->
</assetfiles>
...
<preload> <!-- from jMaki -->
...javascript logic...
</preload>
...
</widget>
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